As one example of a transmission system transmitting content data between plural transmission terminals, a TV conference system for carrying out a TV conference using a communication network such as the Internet may be cited. The necessity of such a TV conference system has been increased along with recent tendency of reducing expenses for business trips and periods of time for business trips. In such a TV conference system, plural TV conference terminals, as examples of transmission terminals, are used. Then, as a result of image data and voice data being transmitted between these TV conference terminals, a TV conference is realized.
Further, along with recent enhancement of broadband environments, high-image-quality image data and/or high-voice-quality voice data can be transmitted. Thereby, it is possible to easily understand situations of other members of a TV conference, and improve fullness of understanding each other via conversations.
However, in a case where many TV conferences are being held via a common communication network or in a case where image data and voice data are received via a narrow band path, a delay may occur in receiving image data and voice data. It is said that when a delay of 0.5 seconds or more occurs in receiving image data or voice data, a user of a TV conference may feel stress during conversation. Therefore, even with recent enhanced broadband environments, there may be a case where a TV conference satisfying users cannot be held.
Further, in a recent TV conference system, for each of plural LANs (Local Area Networks) in a communication network, a relay apparatus that relays image data and voice data between TV conference terminals is provided. These relay apparatuses share necessary communication processes of a TV conference so that a load of each relay apparatus can be reduced, and also, a data transmission amount of image data and voice data to be relayed can be shared.
In the related art, when one of the plural relay apparatuses is selected and used, the relay apparatus used is connected to a LAN to which the TV conference terminal used for the TV conference is also connected. That is, by selecting the relay apparatus having an IP address close to an IP address of the TV conference terminal, it is possible to receive high-image-quality image data or such via the selected relay apparatus (see Japanese Laid-Open Patent Application No. 2008-227577).
In the TV conference system in the related art, the relay apparatus having an IP address close to an IP address of the TV conference terminal used for the TV conference is selected under a supposition that it is possible to receive high-image-quality image data and high-voice-quality voice data via the relay apparatus having an IP address close to an IP address of the TV conference terminal used for the TV conference. However, such a supposition may not necessarily be in accordance with the actual communication network environments. That is, although the relay apparatus having an IP address close to an IP address of the TV conference terminal is used, communication between the TV conference terminal and the relay apparatus may not be available because of an existence a firewall therebetween, or so.